The present invention relates to an emergency isolation valve apparatus on a flow path or a pipeline in an oil refining plant and especially to an emergency isolation valve for checking motion of a valve plug during operation of equipment such as a plant.
In an emergency isolation valve, a valve plug is opened when a plant normally operates, and if abnormality occurs owing to earthquake, the valve plug is shut down to prevent any accidents. Whether the emergency isolation valve properly operates is periodically checked, and it is required to inspect it even during operation of the plant to improve reliability.
Japanese Patent Pub. No.2002-71039A discloses a weight-type emergency isolation valve. A valve plug is checked only at full opening and full closing, but cannot be inspected during operation.
To solve such disadvantage, Japanese Patent Pub. No.10-61812A discloses an emergency isolation valve in which a check valve or a solenoid selector valve for supplying pressurized oil to a cylinder for driving an emergency isolation valve is actually operated for checking their operations. But it is impossible to check whether or not a valve plug itself properly operates. If a valve plug or casing should be corroded internally with fluid to make movement of the valve plug unsmooth, it is unlikely to shut down a fluid path in emergency.